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    <title>Earthquake Clusters</title>
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          <h4 id="title">Earthquake Clusters</h4>
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          <p id="shortdesc">Demonstrates the use of style geometries to render source features of a cluster.</p>
          <div id="docs"><p>This example parses a KML file and renders the features as clusters on a vector layer.  The styling in this example is quite involved. Single earthquake locations (rendered as stars) have a size relative to their magnitude. Clusters have an opacity relative to the number of features in the cluster, and a size that represents the extent of the features that make up the cluster. When clicking or hovering on a cluster, the individual features that make up the cluster will be shown.</p> <p>To achieve this, we make heavy use of style functions and <code>ol.style.Style#geometry</code>.</p>
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          <div id="api-links">Related API documentation: <ul class="inline"><li><a href="../apidoc/ol.Map.html" title="API documentation for ol.Map">ol.Map</a></li>,<li><a href="../apidoc/ol.View.html" title="API documentation for ol.View">ol.View</a></li>,<li><a href="../apidoc/ol.extent.html" title="API documentation for ol.extent">ol.extent</a></li>,<li><a href="../apidoc/ol.format.KML.html" title="API documentation for ol.format.KML">ol.format.KML</a></li>,<li><a href="../apidoc/ol.interaction.html" title="API documentation for ol.interaction">ol.interaction</a></li>,<li><a href="../apidoc/ol.interaction.Select.html" title="API documentation for ol.interaction.Select">ol.interaction.Select</a></li>,<li><a href="../apidoc/ol.layer.Tile.html" title="API documentation for ol.layer.Tile">ol.layer.Tile</a></li>,<li><a href="../apidoc/ol.layer.Vector.html" title="API documentation for ol.layer.Vector">ol.layer.Vector</a></li>,<li><a href="../apidoc/ol.source.Cluster.html" title="API documentation for ol.source.Cluster">ol.source.Cluster</a></li>,<li><a href="../apidoc/ol.source.Stamen.html" title="API documentation for ol.source.Stamen">ol.source.Stamen</a></li>,<li><a href="../apidoc/ol.source.Vector.html" title="API documentation for ol.source.Vector">ol.source.Vector</a></li>,<li><a href="../apidoc/ol.style.Circle.html" title="API documentation for ol.style.Circle">ol.style.Circle</a></li>,<li><a href="../apidoc/ol.style.Fill.html" title="API documentation for ol.style.Fill">ol.style.Fill</a></li>,<li><a href="../apidoc/ol.style.RegularShape.html" title="API documentation for ol.style.RegularShape">ol.style.RegularShape</a></li>,<li><a href="../apidoc/ol.style.Stroke.html" title="API documentation for ol.style.Stroke">ol.style.Stroke</a></li>,<li><a href="../apidoc/ol.style.Style.html" title="API documentation for ol.style.Style">ol.style.Style</a></li>,<li><a href="../apidoc/ol.style.Text.html" title="API documentation for ol.style.Text">ol.style.Text</a></li></ul></div>
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          <textarea class="hidden" name="title">Earthquake Clusters</textarea>
          <textarea class="hidden" name="description">Demonstrates the use of style geometries to render source features of a cluster.</textarea>
          <textarea class="hidden" name="js">var earthquakeFill &#x3D; new ol.style.Fill({
  color: &#x27;rgba(255, 153, 0, 0.8)&#x27;
});
var earthquakeStroke &#x3D; new ol.style.Stroke({
  color: &#x27;rgba(255, 204, 0, 0.2)&#x27;,
  width: 1
});
var textFill &#x3D; new ol.style.Fill({
  color: &#x27;#fff&#x27;
});
var textStroke &#x3D; new ol.style.Stroke({
  color: &#x27;rgba(0, 0, 0, 0.6)&#x27;,
  width: 3
});
var invisibleFill &#x3D; new ol.style.Fill({
  color: &#x27;rgba(255, 255, 255, 0.01)&#x27;
});

function createEarthquakeStyle(feature) {
  // 2012_Earthquakes_Mag5.kml stores the magnitude of each earthquake in a
  // standards-violating &lt;magnitude&gt; tag in each Placemark.  We extract it
  // from the Placemark&#x27;s name instead.
  var name &#x3D; feature.get(&#x27;name&#x27;);
  var magnitude &#x3D; parseFloat(name.substr(2));
  var radius &#x3D; 5 + 20 * (magnitude - 5);

  return new ol.style.Style({
    geometry: feature.getGeometry(),
    image: new ol.style.RegularShape({
      radius1: radius,
      radius2: 3,
      points: 5,
      angle: Math.PI,
      fill: earthquakeFill,
      stroke: earthquakeStroke
    })
  });
}

var maxFeatureCount, vector;
function calculateClusterInfo(resolution) {
  maxFeatureCount &#x3D; 0;
  var features &#x3D; vector.getSource().getFeatures();
  var feature, radius;
  for (var i &#x3D; features.length - 1; i &gt;&#x3D; 0; --i) {
    feature &#x3D; features[i];
    var originalFeatures &#x3D; feature.get(&#x27;features&#x27;);
    var extent &#x3D; ol.extent.createEmpty();
    var j, jj;
    for (j &#x3D; 0, jj &#x3D; originalFeatures.length; j &lt; jj; ++j) {
      ol.extent.extend(extent, originalFeatures[j].getGeometry().getExtent());
    }
    maxFeatureCount &#x3D; Math.max(maxFeatureCount, jj);
    radius &#x3D; 0.25 * (ol.extent.getWidth(extent) + ol.extent.getHeight(extent)) /
        resolution;
    feature.set(&#x27;radius&#x27;, radius);
  }
}

var currentResolution;
function styleFunction(feature, resolution) {
  if (resolution !&#x3D; currentResolution) {
    calculateClusterInfo(resolution);
    currentResolution &#x3D; resolution;
  }
  var style;
  var size &#x3D; feature.get(&#x27;features&#x27;).length;
  if (size &gt; 1) {
    style &#x3D; new ol.style.Style({
      image: new ol.style.Circle({
        radius: feature.get(&#x27;radius&#x27;),
        fill: new ol.style.Fill({
          color: [255, 153, 0, Math.min(0.8, 0.4 + (size / maxFeatureCount))]
        })
      }),
      text: new ol.style.Text({
        text: size.toString(),
        fill: textFill,
        stroke: textStroke
      })
    });
  } else {
    var originalFeature &#x3D; feature.get(&#x27;features&#x27;)[0];
    style &#x3D; createEarthquakeStyle(originalFeature);
  }
  return style;
}

function selectStyleFunction(feature) {
  var styles &#x3D; [new ol.style.Style({
    image: new ol.style.Circle({
      radius: feature.get(&#x27;radius&#x27;),
      fill: invisibleFill
    })
  })];
  var originalFeatures &#x3D; feature.get(&#x27;features&#x27;);
  var originalFeature;
  for (var i &#x3D; originalFeatures.length - 1; i &gt;&#x3D; 0; --i) {
    originalFeature &#x3D; originalFeatures[i];
    styles.push(createEarthquakeStyle(originalFeature));
  }
  return styles;
}

vector &#x3D; new ol.layer.Vector({
  source: new ol.source.Cluster({
    distance: 40,
    source: new ol.source.Vector({
      url: &#x27;https://openlayers.org/en/v4.6.5/examples/data/kml/2012_Earthquakes_Mag5.kml&#x27;,
      format: new ol.format.KML({
        extractStyles: false
      })
    })
  }),
  style: styleFunction
});

var raster &#x3D; new ol.layer.Tile({
  source: new ol.source.Stamen({
    layer: &#x27;toner&#x27;
  })
});

var map &#x3D; new ol.Map({
  layers: [raster, vector],
  interactions: ol.interaction.defaults().extend([new ol.interaction.Select({
    condition: function(evt) {
      return  evt.type &#x3D;&#x3D; &#x27;pointermove&#x27; ||
          evt.type &#x3D;&#x3D; &#x27;singleclick&#x27;;
    },
    style: selectStyleFunction
  })]),
  target: &#x27;map&#x27;,
  view: new ol.View({
    center: [0, 0],
    zoom: 2
  })
});
</textarea>
          <textarea class="hidden" name="css">#map {
  position: relative;
}
#info {
  position: absolute;
  height: 1px;
  width: 1px;
  z-index: 100;
}
.tooltip.in {
  opacity: 1;
}
.tooltip.top .tooltip-arrow {
  border-top-color: white;
}
.tooltip-inner {
  border: 2px solid white;
}
</textarea>
          <textarea class="hidden" name="html">&lt;div id&#x3D;&quot;map&quot; class&#x3D;&quot;map&quot;&gt;&lt;/div&gt;
</textarea>
          <input type="hidden" name="resources" value="https://openlayers.org/en/v4.6.5/css/ol.css,https://openlayers.org/en/v4.6.5/build/ol.js">
          <input type="hidden" name="data">
        </form>
        <pre><code id="example-source" class="language-markup">&lt;!DOCTYPE html&gt;
&lt;html&gt;
  &lt;head&gt;
    &lt;title&gt;Earthquake Clusters&lt;/title&gt;
    &lt;link rel="stylesheet" href="https://openlayers.org/en/v4.6.5/css/ol.css" type="text/css"&gt;
    &lt;!-- The line below is only needed for old environments like Internet Explorer and Android 4.x --&gt;
    &lt;script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL"&gt;&lt;/script&gt;
    &lt;script src="https://openlayers.org/en/v4.6.5/build/ol.js"&gt;&lt;/script&gt;
    &lt;style&gt;
      #map {
        position: relative;
      }
      #info {
        position: absolute;
        height: 1px;
        width: 1px;
        z-index: 100;
      }
      .tooltip.in {
        opacity: 1;
      }
      .tooltip.top .tooltip-arrow {
        border-top-color: white;
      }
      .tooltip-inner {
        border: 2px solid white;
      }
    &lt;/style&gt;
  &lt;/head&gt;
  &lt;body&gt;
    &lt;div id&#x3D;&quot;map&quot; class&#x3D;&quot;map&quot;&gt;&lt;/div&gt;
    &lt;script&gt;
      var earthquakeFill &#x3D; new ol.style.Fill({
        color: &#x27;rgba(255, 153, 0, 0.8)&#x27;
      });
      var earthquakeStroke &#x3D; new ol.style.Stroke({
        color: &#x27;rgba(255, 204, 0, 0.2)&#x27;,
        width: 1
      });
      var textFill &#x3D; new ol.style.Fill({
        color: &#x27;#fff&#x27;
      });
      var textStroke &#x3D; new ol.style.Stroke({
        color: &#x27;rgba(0, 0, 0, 0.6)&#x27;,
        width: 3
      });
      var invisibleFill &#x3D; new ol.style.Fill({
        color: &#x27;rgba(255, 255, 255, 0.01)&#x27;
      });

      function createEarthquakeStyle(feature) {
        // 2012_Earthquakes_Mag5.kml stores the magnitude of each earthquake in a
        // standards-violating &lt;magnitude&gt; tag in each Placemark.  We extract it
        // from the Placemark&#x27;s name instead.
        var name &#x3D; feature.get(&#x27;name&#x27;);
        var magnitude &#x3D; parseFloat(name.substr(2));
        var radius &#x3D; 5 + 20 * (magnitude - 5);

        return new ol.style.Style({
          geometry: feature.getGeometry(),
          image: new ol.style.RegularShape({
            radius1: radius,
            radius2: 3,
            points: 5,
            angle: Math.PI,
            fill: earthquakeFill,
            stroke: earthquakeStroke
          })
        });
      }

      var maxFeatureCount, vector;
      function calculateClusterInfo(resolution) {
        maxFeatureCount &#x3D; 0;
        var features &#x3D; vector.getSource().getFeatures();
        var feature, radius;
        for (var i &#x3D; features.length - 1; i &gt;&#x3D; 0; --i) {
          feature &#x3D; features[i];
          var originalFeatures &#x3D; feature.get(&#x27;features&#x27;);
          var extent &#x3D; ol.extent.createEmpty();
          var j, jj;
          for (j &#x3D; 0, jj &#x3D; originalFeatures.length; j &lt; jj; ++j) {
            ol.extent.extend(extent, originalFeatures[j].getGeometry().getExtent());
          }
          maxFeatureCount &#x3D; Math.max(maxFeatureCount, jj);
          radius &#x3D; 0.25 * (ol.extent.getWidth(extent) + ol.extent.getHeight(extent)) /
              resolution;
          feature.set(&#x27;radius&#x27;, radius);
        }
      }

      var currentResolution;
      function styleFunction(feature, resolution) {
        if (resolution !&#x3D; currentResolution) {
          calculateClusterInfo(resolution);
          currentResolution &#x3D; resolution;
        }
        var style;
        var size &#x3D; feature.get(&#x27;features&#x27;).length;
        if (size &gt; 1) {
          style &#x3D; new ol.style.Style({
            image: new ol.style.Circle({
              radius: feature.get(&#x27;radius&#x27;),
              fill: new ol.style.Fill({
                color: [255, 153, 0, Math.min(0.8, 0.4 + (size / maxFeatureCount))]
              })
            }),
            text: new ol.style.Text({
              text: size.toString(),
              fill: textFill,
              stroke: textStroke
            })
          });
        } else {
          var originalFeature &#x3D; feature.get(&#x27;features&#x27;)[0];
          style &#x3D; createEarthquakeStyle(originalFeature);
        }
        return style;
      }

      function selectStyleFunction(feature) {
        var styles &#x3D; [new ol.style.Style({
          image: new ol.style.Circle({
            radius: feature.get(&#x27;radius&#x27;),
            fill: invisibleFill
          })
        })];
        var originalFeatures &#x3D; feature.get(&#x27;features&#x27;);
        var originalFeature;
        for (var i &#x3D; originalFeatures.length - 1; i &gt;&#x3D; 0; --i) {
          originalFeature &#x3D; originalFeatures[i];
          styles.push(createEarthquakeStyle(originalFeature));
        }
        return styles;
      }

      vector &#x3D; new ol.layer.Vector({
        source: new ol.source.Cluster({
          distance: 40,
          source: new ol.source.Vector({
            url: &#x27;https://openlayers.org/en/v4.6.5/examples/data/kml/2012_Earthquakes_Mag5.kml&#x27;,
            format: new ol.format.KML({
              extractStyles: false
            })
          })
        }),
        style: styleFunction
      });

      var raster &#x3D; new ol.layer.Tile({
        source: new ol.source.Stamen({
          layer: &#x27;toner&#x27;
        })
      });

      var map &#x3D; new ol.Map({
        layers: [raster, vector],
        interactions: ol.interaction.defaults().extend([new ol.interaction.Select({
          condition: function(evt) {
            return  evt.type &#x3D;&#x3D; &#x27;pointermove&#x27; ||
                evt.type &#x3D;&#x3D; &#x27;singleclick&#x27;;
          },
          style: selectStyleFunction
        })]),
        target: &#x27;map&#x27;,
        view: new ol.View({
          center: [0, 0],
          zoom: 2
        })
      });
    &lt;/script&gt;
  &lt;/body&gt;
&lt;/html&gt;</code></pre>
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